The present invention relates to a wireless tire condition monitoring apparatus that permits a driver in a vehicle passenger compartment to check the conditions of tires, such as the air pressure. More specifically, the present invention relates to a transmitter in a tire condition monitoring apparatus.
Some transmitters for tire condition monitoring apparatus have a valve stem that is formed integrally with a casing and functions as a transmission antenna. The casing accommodates electronic elements for transmitting data, which data represents the condition of a tire. Such a casing includes a flange extending outward from the bottom and triangular reinforcing ribs between the flange and the outer surface of the casing. Therefore, when the tire is replaced, the tire beads are overlaid on the casing. Therefore, the tire is replaced without damaging the casing (Japanese Laid-Open Patent Publication No. 2000-081358).
However, the construction disclosed in the publication cannot be applied to all the types of vehicle wheels. That is, there are many different types of cross-sectional shapes in wheels. The cross-sectional shapes in wheels include a deep rim, a shallow rim, a wide flat rim, and wide deep rim. Therefore, the angle defined by a valve stem and a casing is determined by the cross-sectional shape of a wheel. As a result, to attach a casing to a drop center of a wheel, a valve for a transmitter in a tire condition monitoring apparatus must correspond to the cross-sectional shape of the wheel.